1. Field of the Invention
The present invention relates to a ground-to-air telephone system which permits a ground based caller to establish telephonic communication with an airborne telephone of unknown location.
2. Background Information
Airborne telephone systems are well known and widely used. Such systems are typically utilized by a passenger on an aircraft to initiate a telephone call to a ground based party connected to the public switched telephone network (PSTN). Through such systems, an airborne party can initiate telephone calls to any telephone in the world. Such calls are transmitted from the airborne telephone to ground stations which route the telephone calls by way of the PSTN to the called party.
However, if a ground based party wishes to call an airborne telephone using such a system, the ground based party must know which specific ground station is within transmission range of the aircraft. This requirement necessitates that the ground based party know the particular location of the aircraft at any given time, thereby presenting prohibitive mapping requirements. As a result, ground-to-air telephone calls are seldom attempted because of the unfeasibility of knowing the particular location of an aircraft at any given time.
Mobile ground telephone systems, such as cellular systems, are known, wherein a central location coordinates the selection of calls, i.e., the central location selects which ground station is in communication with the mobile telephone and routes and completes the call accordingly. Such mobile ground systems are inadequate for airborne use, however, because the use of such a central location in airborne applications causes inadequate contention between ground stations for the selection of channel frequencies.